Plus, why should we eat what our ancestors ate anyway - if we know of a better option now?The argument 'but our ancestors ate meat' makes no sense. Our ancestors probably flung feces at each other and dragged women into their caves by the hair to rape them repeatedly.
Both in South India, + some areas in the North East and North-West, there aren't only strong vegetarian traditions, but also many who avoid dairy products.
Here are two articles about an Indian who eats vegetarian food (he eats a little dairy sometimes), but is still going strong. He started participating in the London Marathon when he was 89, but will stop doing marathons after tomorrow, when he will participate in the Hong Kong marathon, five weeks before his 102nd birthday - but he "fully intends to continue running for pleasure".